Adding GRUB_CMDLINE_LINUX="nomodeset acpi_backlight=vendor" in /etc/default/grub and running update-grub works as a workaround for me too.
-- Screen brightness does not function on Acer Aspire Timeline 5810TZ https://bugs.launchpad.net/bugs/438537 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
